Along with the development of 3D TV technology, the technique of generating multi-view images by using a small number of 2D images has become increasingly important. Nowadays, many techniques are developed for generating virtual view images, and those techniques can be categorized into two groups. The first group is to generate the images of other virtual views based on one image, and the other group is to generate the images of the virtual views within an angle formed by two images by using these two images. The virtual views simulated by using each of aforementioned techniques with small unknown regions due to the small angle transformation. However, the image content displayed on an auto-stereoscopic 3D TV is required to simulate the large angle transformation of virtual views and accordingly generate very large unknown regions, which is not acceptable to the techniques mentioned above. To generate lifelike virtual view images, besides image simulation, the processing of disparity map is also very important, in which whether the values of the pixels in the disparity map are correct determines whether an image can be projected to the correct position, and the hole filling of unknown regions in the disparity map of virtual views also affects the correctness of image information.
Most existing hole-filling techniques are adapted to filling holes in small unknown region generated through small angle transformation. When the transformed angle increases, the area of the unknown region also increases. In some case, the left-right relation of the foreground and the background may be changed after the large angle transformation. As a result, there is no correct disparity value around the unknown region and only incorrect value can be captured from adjacent regions. For example, FIG. 1 illustrates a disparity map obtained after large angle transformation. Referring to FIG. 1, the portion of lighter color represents that the object is closer to the capturing position, while the portion of darker color represents that the object is farther to the capturing position. The unknown region 18 (in black color) is originally the background of the plaster model 14, and the disparity of this region should be the same as the background 12 of the disparity map. However, the unknown region 18 produced through the view transformation is located between the plaster model 14 and the triangular pyramid 16. The unknown region 18 is completely surrounded by the foreground and therefore is not connected to the correct background.
Additionally, in a general hole-filling method, holes at different virtual views are respectively filled. Thus, a same spot in the 3D space may be filled with different disparity value at different virtual views. As a result, the 3D effect is affected.